BACKGROUND: Postsystolic shortening (PSS) has been proposed as a marker of myocardial dysfunction. Strain rate imaging (SRI) is a novel ultrasonic technique, allowing reliable and noninvasive measurement of myocardial deformation. The purpose of this study was to investigate the characteristics of myocardial longitudinal PSS by SRI in ischemic and infarct myocardium in patients with coronary artery disease, and to explore its clinical applicability. METHODS: Eleven patients with angina pectoris, 21 patients with myocardial infarction and 20 healthy subjects were included in the study. Apical four-, three- and two-chamber views were displayed; and septal, lateral, anteroseptal, posterior, anterior and inferior walls of the left ventricle were scanned, respectively. PSS strain (epsilon(pss)), the ratio of epsilon(pss) and systolic strain (epsilon(pss)/epsilon(sys)), the ratio of epsilon(pss) and maximum strain (epsilon(pss)/epsilon(max)) and the duration of PSS (T(pss)) in ischemic, infarct and normal myocardium were analyzed. RESULTS: PSS was found more frequent in the ischemic and infarct segments compared with the normal segments (39% vs 22% and 56% vs 22%, respectively; both P < 0.01). It was even more frequent in the infarct segments than in the ischemic segments (56% vs 39%, P < 0.01). The absolute magnitude of epsilon(pss), epsilon(pss)/epsilon(sys), epsilon(pss)/epsilon(max) were significantly larger and T(pss) significantly longer in the ischemic and infarct segments compared with that in the normal myocardium (P < 0.01). epsilon(pss)/epsilon(sys), epsilon(pss)/epsilon(max) were even larger and T(pss) even longer in the infarct than in the ischemic segments (P < 0.01). CONCLUSIONS: PSS is a common and important feature of the ischemic and infarct myocardium. epsilon(pss), epsilon(pss)/epsilon(sys), epsilon(pss)/epsilon(max) and T(pss) as measured by SRI may be promising markers for the quantitative assessment of regional myocardial dysfunction in patients with coronary artery disease. epsilon(pss)/epsilon(sys), epsilon(pss)/epsilon(max) and T(pss) may be helpful in differentiating infarct from ischemic myocardium.